Method of removing tacky substance or waste liquid containing tacky substance

ABSTRACT

A method of removing a sticky substance or a waste liquid containing a sticky substance which comprises, mixing a solid substance having inflammability and liquid-absorptivity into the sticky substance or the waste liquid containing the sticky substance wherein these are mixed to allow a liquid component of the sticky substance or the waste liquid containing the sticky substance to be absorbed into the solid substance and to allow the sticky substance to be entangled with the solid substance, and then removing the sticky substance together with the solid substance.

TECHNICAL FIELD

The present invention relates to a method of easily removing, forexample, waste liquid containing a sticky substance by-produced in areaction process of petrochemical process, liquid (waste liquid)containing a partially polymerized substance (sticky substance)generated in a process of production and storage of aneasily-polymerizable substance.

BACKGROUND ART

A sticky substance is by-produced in a reaction process of petrochemicalprocess, and waste liquid containing the sticky substance is extremelydifficult to be removed due to its stickiness. Usually, the stickysubstance is removed by methods such as dissolving by a solvent. In aprocess of producing and storing an easily-polymerizable substance, apartially polymerized substance is generated. The process liquidcontaining the partially polymerized substance (sticky substance) isalso removed as waste liquid, usually, by methods such as dissolving bya solvent (see, Japanese Patent Application Laid-Open (JP-A) No.2000-290225). If the stickiness is lower to a certain extent, the wasteliquid is fed as it is to an incinerator by a pump without using asolvent, and then it is burned. The steam is recovered from wasteliquid, thus, waste liquid can be treated economically and efficientlyin some cases.

However, if the stickiness is higher to a certain extent, a largeramount of solvent is generally necessary as compared with the amount ofwaste liquid. Therefore, cost required for a solvent itself, anddeterioration in working environments because of harmfulness andvolatility of the solvent, are often problematical. It is apparent thatrecovering a large amount of solvent after dissolution and burning thisgives energy waste. Particularly, process liquid containing apolymerized substance generated in an equipment for producing methyl(meth)acrylate and (meth)acrylic acid contains by-products having highstickiness and showing solid-like nature in some cases. Among them,there are not a few substances poorly-soluble in a solvent. Such processliquid is impossible to be lifted by a pump in some cases.

In the specification of the instant application, (meth)acrylic acid isgeneric name for acrylic acid and methacrylic acid. Methyl(meth)acrylate is generic name for methyl acrylate and methylmethacrylate.

Removal of liquid containing such a sticky substance from a vessel isdisadvantage from the standpoints of cost, working environment or energysaving in conventional methods using a solvent, and complete removalthereof is difficult.

DISCLOSURE OF INVENTION

An object of the present invention is, in the case of removal of asticky substance or waste liquid containing a sticky substance from avessel and the like which has been conventionally difficult, to providea method which makes the removal work easy and can perform also thesubsequent burning treatment at low cost and easily.

The present invention provides a method of removing a sticky substanceor a waste liquid containing a sticky substance which comprises mixing asolid substance having inflammability and liquid-absorptivity into thesticky substance or the waste liquid containing the sticky substancewherein these are mixed to allow a liquid component of the stickysubstance or the waste liquid containing the sticky substance to beabsorbed into the solid substance and to allow the sticky substance tobe entangled with the solid substance,

and then removing the sticky substance together with the solidsubstance.

In the present invention, since a liquid component is absorbed into anda sticky substance is entangle with such a solid substance, the resultedmixture can be handled as if it is solid. For example, it can beefficiently and almost completely removed from a vessel by a scoop, andthen it can be easily packed. Furthermore, the sticky substanceentangled with the solid substance after removal from a vessel can be,for example, put into an incinerator and burnt completely. Therefore,the present invention is by far advantageous as compared with casesusing noncombustibles such as sand and advantageous from the standpointsof working environments and energy saving as compared with a case usinga solvent.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, a solid substance having inflammability andliquid-absorptivity is used in order to remove a sticky substance orwaste liquid containing a sticky substance from a vessel and the like inmaintenance or cleaning of various production equipments and storageequipments.

Here, the sticky substance or waste liquid containing a sticky substanceincludes not only a sticky substance or waste liquid containing a stickysubstance by-produced in a reaction process of petrochemical process,but also, for example, a partially polymerized substance or processliquid containing a partially polymerized substance generated in aprocess of production, distillation, purification or storage of aeasily-polymerizable substance. The method of the present invention isvery useful particularly in the case of removal as waste liquid of apartially polymerized substance or process liquid containing a partiallypolymerized substance discharged from an equipment for producing methyl(meth)acrylate and/or (meth)acrylic acid.

The solid substance having inflammability and liquid-absorptivity is notparticularly restricted, and it is preferable to use substances of whichraw material is cheap and which give no harmfulness, can be obtainedeasily and can be present on a routine basis. The shape thereof may beparticle, flake, fiber, powder, chip, string, thread, noodle and thelike. Specifically, a fractured substance made of wood (e.g., sawdust)is preferable since it is cheap and obtainable easily and has noharmfulness. In addition to the fractured substance made of wood, forexample, a cut substance made of paper (e.g., shredder dust) can be usedas a solid substance having inflammability and liquid-absorptivity.

In maintenance or cleaning of a vessel storing waste liquid, forexample, first, liquid having stickiness relatively lower so that it canbe discharged from a vessel under head pressure is discharged from adischarging port and received by another vessel. A solid substancehaving inflammability and liquid-absorptivity is added to this liquidhaving lower stickiness discharged into another vessel. These are mixedby a scoop, stirring rod, stirrer or the like. By mixing, the solidsubstance absorbs a liquid component, and the sticky substance isentangled with the solid substance, to lower stickiness and to givehandling like solid. The sticky substance provided with handling likesolid may be advantageously packed by, for example, a scoop.

The vessel for storing waste liquid after removal of liquid havingrelatively lower stickiness usually contains liquid having relativelyhigher stickiness left. Regarding the residue remaining at the bottom ofsuch a vessel, for example, it is advantageous that a solid substancehaving inflammability and liquid-absorptivity is dispersed in thevessel, mixed by a scoop, and packed to be discharged out of the vesselin the same manner.

Then, the packed waste liquid removed out of the vessel can be burnt asit is. A sticky substance remaining in the vessel in slight amount canbe easily wiped away by a waste cloth.

In the present invention, the amount of a solid substance havinginflammability and liquid-absorptivity is not particularly restricted,and the amount may be such that a liquid component is absorbedsufficiently so as to give handling like solid and stickiness can belowered.

The present invention will be illustrated further in detail by examplesbelow, but they are only exemplary and dot not limit the scope of theinvention at all.

EXAMPLE

As described bellow, the cleaning was performed of a tank for storingwaste liquid of a process of continuously synthesizing methylmethacrylate and methacrylic acid, wherein acetonecyanhydrin reactedwith sulfuric acid to produce methacrylamide sulfate and then it reactedwith water and methanol.

First, most of the residue in tank was discharged, and the residualliquid containing a sticky polymerized substance mainly composed ofmethacrylic acid was leaved in tank. The discharged liquid containing apolymerized substance which had stickiness so lower as to be dischargedfrom the tank discharging port under head pressure was received by abasin. Then, a fractured substance made of wood (i.e., sawdust) wasdispersed on the discharged liquid in the basin, and they were mixed bya scoop. When the fracture substance made of wood absorbed a liquidcomponent and the sticky polymerized substance mainly composed ofmethacrylic acid was entangled with the fracture substance made of woodand resultantly the mixture got easy handling by a scoop approximatelylike solid, the mixture was packed in a plastic bag. Thus, the wasteliquid discharged from the discharging port could be completely packed.

On the other hand, a polymerized substance mainly composed ofmethacrylic acid having stickiness so high as to give poor dischargingfrom the tank discharging port remained at the bottom of the tank. Here,a fractured substance made of wood (i.e., sawdust) was dispersed in thetank and mixed by a scoop, and then packed in the same manner to beremoved outside. The sticky polymerized substance packed did not leak asliquid even if a pore is made on the bag.

Furthermore, a slight amount of sticky polymerized substance adhere onthe bottom and wall surface of the tank was wiped away by waste cloth toperform a cleaning approximately completely the inside of the tank.Then, the packed sticky polymerized substance removed out of the tankand the waste liquid containing the polymerized substance were chargedinto an incinerator capable of burning solid, and all of them could beburnt.

In the above-mentioned packing operation, the polymerized substanceadhered to a rubber glove to cause pollution. However, when thefractured substance made of wood (i.e., sawdust) was grasped once andboth hands were rubbed mutually, the polymerized substance was entangledwith the fractured substance made of wood and consequently the glovecould be cleaned easily.

The fractured substance made of wood (i.e., sawdust) used in thisexample was purchased from a lumber mill at low cost and had a sizegenerally available.

COMPARATIVE EXAMPLE

The same cleaning in the tank as in Example was performed without usinga solid substance having inflammability and liquid-absorptivity.

First, most of waste liquid was discharged in the same manner as inExample. Here, liquid containing a polymerized substance havingstickiness so lower as to be discharged from a tank under head pressurewas tried to be received by a basin and packed. However, since a scoopcan only scoop up a small amount of substance, a method of receiving bya plastic bag at a discharging port was adopted. As the result, aproblem arose that liquid dripping at the discharging port wassignificant and the sticky polymerized substance adhered on the operatorand the outer surface of the bag to cause pollution. Furthermore, aproblem also arose that the sticky liquid leaked when a pore is made onthe plastic bag.

On the other hand, a polymerized substance mainly composed ofmethacrylic acid having high stickiness remaining on the bottom of thetank was tried to be packed by a scoop in the tank. However, as aresult, cloths of the operator was polluted and the packing operationdid not progress smoothly and stopped on the way due to the stickinessof the polymerized substance, accordingly, the polymerized substancecould not be removed completely.

The waste liquid containing the packed polymerized substance should betreated carefully so as not to injure the bag in charging this into anincinerator capable of burning a solid substance, and the efficiency ofthe charging operation lowered extremely. Furthermore, the polymerizedsubstance adhered onto a rubber glove to cause pollution in the packingoperation, and this was tried to be wiped by waste cloth, however,complete wiping was impossible.

As described above, the present invention can provide a method which, inthe case of removal of a sticky substance or waste liquid containing asticky substance from a vessel and the like which has beenconventionally difficult, makes the removing operation easy, and iscapable of performing also the subsequent burning treatment at low costeasily.

1. A method of removing a sticky substance or a waste liquid containinga sticky substance which comprises: mixing a solid substance havinginflammability and liquid-absorptivity into a sticky substance or awaste liquid containing a sticky substance wherein these are mixed toallow a liquid component of the sticky substance or the waste liquidcontaining the sticky substance to be absorbed into the solid substanceand to allow the sticky substance to be entangled with the solidsubstance, wherein the sticky substance or waste liquid containing thesticky substance is a partially polymerized substance or waste liquidcontaining a partially polymerized substance generated in a process ofproduction, distillation, purification or storage of aneasily-polymerizable substance, and then removing the sticky substancetogether with the solid substance or the waste liquid containing thesticky substance together with the solid substance.
 2. The methodaccording to claim 1, wherein the liquid component of the stickysubstance or the waste liquid containing the sticky substance to beabsorbed into the solid substance are mixed with the solid substance toallow the sticky substance to be entangled with the solid substance, andas a result, stickiness of the mixture is lowered so that the mixturecan be handled like a solid.
 3. The method according to claim 1, whereinthe sticky substance is a partially polymerized substance or the wasteliquid containing the sticky substance is a waste liquid containing apartially polymerized substance discharged from an equipment forproducing methyl methacrylate or methacrylic acid, or both.
 4. Themethod according to claim 1, wherein the sticky substance or the wasteliquid containing the sticky substance is a by-product in a reactionprocess of a petrochemical process.
 5. The method according to claim 1,wherein the solid substance having inflammability andliquid-absorptivity is in the form of a particle, flake, fiber, powder,chip, string, thread or noodle.
 6. The method according to claim 1,wherein the solid substance having inflammability andliquid-absorptivity is a fractured substance made of wood.
 7. The methodaccording to claim 1, wherein the solid substance having inflammabilityand liquid-absorptivity is a cut substance made of paper.
 8. The methodaccording to claim 1, which further comprises discharging the wasteliquid containing the sticky substance from a first vessel to a secondvessel, wherein after discharging said waste liquid, residue is presentin said first vessel, and mixing the solid substance havinginflammability and liquid-absorptivity with the waste liquid in saidsecond vessel.
 9. The method according to claim 2, wherein the mixturewhich can be handled like a solid is packed in a bag.
 10. The methodaccording to claim 8, which comprises mixing the solid substance havinginflammability and liquid-absorptivity with said residue in said firstvessel.
 11. The method according to claim 9, wherein the packed mixtureis burnt.